The present invention relates to a device for unloading catalyst or other particles from the tubes of a chemical reactor.
Many chemical reactors are essentially a large shell and tube heat exchanger vessel, with the reaction occurring inside the tubes and a coolant circulating in the vessel outside the tubes. A chemical reactor vessel also can be a simple tank with a single volume of catalyst inside it, or it may be a single large tube. Some chemical reactions occur in furnace or reformer tubes, which may be a part of a system with 10 to 500 or more such tubes. In any of these reactor vessels, catalyst, typically in the form of pellets, may be loaded into the reactor to facilitate the reaction. The catalyst is replaced periodically.
The reactor tubes may be quite long, housed in a structure several stories tall. In order to replace the catalyst, the old, spent catalyst must first be removed from the reactor tubes. In the prior art, springs are first removed from the bottom of each tube in the reactor and then a fish tape is manually pushed up from the bottom of each tube to jostle the catalyst particles and evacuate each tube.
A fish tape may be a thin piece of flat steel wire or a thin rod or stiff wire that may be coiled in predetermined lengths. It usually is used to help feed wires through a pipe or conduit. When it is used for that purpose, the fish tape is first fished through a pipe or conduit and then, once it reaches the other end, wires are attached to that end, and then the fish tape is pulled back out, which feeds the wires through the pipe or conduit. However, in this instance, the fish tape is used to poke upwardly into the reactor tubes to contact the catalyst particles and jostle them to make them fall out of the tube.
As some of the catalyst particles fall out of the tube, other catalyst particles start to move downwardly but can bridge inside the tube, which prevents them from falling out of the tube. The fish tape is manually pushed in and out repeatedly to break up any bridging and allow the particles to fall out. Sometimes the fish tape is withdrawn entirely from the tube to allow catalyst particles to fall out from the tube. Care must be taken when using a fish tape to ensure that as the particles are dislodged and are in the process of falling out of the tube that they do not jam along with the fish tape and the narrow tube wall. When a fish tape is operated manually by an operator, the operator can only advance the fish tape slowly and tries to keep the fish tape constantly moving so as to not get it stuck or otherwise jammed in the tube with catalyst engulfing a portion of the fish tape such that it can neither be pushed into nor withdrawn from the tube.